Question

In each case explain your reasoning. If you are not sure of your answer, explain why you are uncertain.

When a person lowers a bowling ball at a constant speed is the work by the person on the ball positive, negative or approximately zero?

When a person carries a bowling ball as they walk along a level hallway at constant speed is the work by the person on the ball positive, negative or approximately zero?

When a person carries a bowling ball up a flight of stairs at constant speed is the work by person on the bowling ball positive, negative, or approximately zero?

When a person carries a bowling ball up a flight of stairs at constant speed is the work by the stairs on the person positive, negative, or approximately zero.

Answer 1

a) For first cndition, as we are working with constant speed Work done = Force* displacement, where force= m*a

at constant speed net acceleration is due to gravity so the work by the person will be positive.

b) At level hallway the force component from gravity can be directly neglected as is perpendicular to distance travelled and walking with constant speed will give us net acceleration zero in the given plane. So, work done will be approximately zero.

c) When a person carrier a bowling ball up the incline it does work against the gravity causing -ve work to be done.

d) work done by the stairs on the person will be positive as normal reaction will tend to do work.